Abstract
The St Joseph field, located approximately 135km offshore Sabah Malaysia, was identified as a chemical EOR candidate. The field is undergoing water flood and there are six water injectors. The chemical EOR will utilize the exiting water injectors as well as additional new injectors. The current design of the chemical cocktail is a non-Newtonian fluid that exhibits 3-cp viscosity in the reservoir. The base case injection rate is 10000 bpd into two zones.
In order to achieve the designed injection rate, fractured injection was designed as the base case injection method. Since the viscosity of the chemical cocktail is much higher than that of water, the injectivity and fracture containment were identified as key issues. This paper outlines a simple, yet fit-for-purpose method developed to model the injectivity and injection conformance under the fractured injection conditions using the commercial modeling tool, REVEAL. A box model was constructed with the available geology, reservoir, petrophysical and geomechanical data. Then the box model was calibrated with the dynamic reservoir model to simulate the reservoir pressure behavior during the chemical flood. Finally the fluid rheology data from the laboratory study were applied in the model. Sensitivities of fracture growth to the key input parameters, including stress contrast, injection rate, reservoir properties and injection fluid properties, were examined. The results show that the fracture growth is contained under the base case injection scenario. The fracture containment is sensitive to the injection fluid quality, injection rate and rock mechanic properties. A preliminary operating envelop of the contained injection was defined according to the results. This method is applicable for investigation of the fracture containment for the water and chemical EOR injections for onshore and offshore fields.
